Method of treatment of alzheimer&#39;s disease and device therefor

ABSTRACT

A method and device for treating Alzheimer&#39;s disease (AD) is disclosed. The method involves the removal of circulating autoantibodies of a biochemical marker or markers, specifically human glial fibrillary acidic protein (GFAP) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), in bodily fluid, preferably blood or a blood product. The invention further includes a device or process of immune system modulation effective for autoantibody removal.

FIELD OF THE INVENTION

[0001] The present invention relates to a method for the treatment ofAlzheimer's disease (AD). The invention particularly relates to aprocess for removing the presence of at least one biochemical marker inthe blood associated with Alzheimer's disease. More particularly, theinvention relates to a device which specifically binds to circulatingautoantibodies, said antibodies ultimately being removed from the bloodof a patient suffering from Alzheimer's disease.

BACKGROUND OF THE INVENTION

[0002] Alzheimer's disease, also referred to as Alzheimer's dementia orAD is a progressive neurodegenerative disorder that causes memory lossand serious mental deterioration. Diagnosticians have long sought ameans to definitively identify AD during the lifetime of dementedpatients, as opposed to histopathological examination of brain tissue,which is the only present means available for rendering an ultimatediagnosis of AD. AD is the most common form of dementia, accounting formore than half of all dementias and affecting as many as 4 millionAmericans and nearly 15 million people worldwide. Dementia may startwith slight memory loss and confusion, but advances with time reachingsevere impairment of intellectual and social abilities. At age 65, thecommunity prevalence of AD is between 1-2%. By age 75, the figure risesto 7%, and by age 85 it is 18%. The prevalence of dementia in allindividuals over age 65 is 8%. Of those residing in institutions, theprevalence is about 50%, at any age.

[0003] The social impact of this disease is enormous, caused by theburden placed on caregivers, particularly in the latter stages of thedisease. The substantial economic costs are largely related tosupportive care and institutional admission. The rapidly increasingproportion of elderly people in society means that the number ofindividuals affected with AD will grow dramatically, therefore findingan early accurate diagnosis and a cure for AD is becoming an issue ofmajor importance world wide.

[0004] When an individual is suspected of AD, several recommended testsare performed : (1) Mini Mental State Examination (MMSE)—an office-basedpsychometric test in the form of a Functional Assessment Questionnaire(FAQ) to examine the scale for functional autonomy, (2) Laboratorytests—complete blood count, measurement of thyroid stimulating hormone,serum electrolytes, serum calcium and serum glucose levels, (3)Neuroimaging—most commonly used is computed tomography (CT) which has arole in detecting certain causes of dementia such as vascular dementia(VaD), tumor, normal pressure hydrocephalus or subdural hematoma.However, neuroimaging is less effective in distinguishing AD or othercortical dementias from normal aging. In primary care settings, somesuggest that CT could be limited to atypical cases, but others recommendroutine scanning. Magnetic resonance imaging (MRI) currently offers noadvantage over CT in most cases of dementia.

[0005] While Alzheimer's is the most common form of dementia, accountingfor at least 60% of cases, diagnostic procedures for determining theexact cause of dementia, among more than 80 different species, isdifficult at best.

[0006] In comparison to other disease areas, the field of dementiaraises questions concerning the value of diagnosis, since there iscurrently no cure or effective therapy available. In dementia, as in allother branches of medicine, the certainty of a diagnosis has animportant impact on the management of the patient. While AD cannot becured at present time, there is symptomatic treatment available and thefirst drugs (acetylcholinesterase inhibitors) for the temporaryimprovement of cognition and behavior are now licensed by the U.S. Foodand Drug Administration. Other drugs are at different stages of clinicaltrials: (1) Drugs to prevent decline in AD—DESFERRIOXAMINE, ALCAR,anti-inflammatory drugs, antioxidants, estrogen, (2) NeurotrophicFactors: NGF, (3) Vaccine : the recent most exciting report by Schenk etal. (Nature 1999;400:173-7) raises the hope of a vaccine for AD.Unfortunately, a percentage of patients cannot tolerate thepharmaceutical agents currently made available due to allergicreactions, drug interactions, genetic inability to properly metabolizethe agent, or the like, and therefore are unable to utilize themedicinal advantages of these agents. In addition, the pharmaceuticalagents themselves have limited therapeutic value. After a length oftime, the agent no longer is able to function as intended due to thebody's tolerance, resulting in the buildup of autoantibodies. In thiscase, alternate therapy to control the level of autoantibodiescirculating in the body by periodic removal may increase the length oftime of an agent's medicinal value.

[0007] The specificity of the various therapies thus requiresophisticated diagnostic methodologies, having a high degree ofsensitivity for AD, in order to insure their success.

[0008] Currently there are a multitude of tests available which aid inthe diagnosis of AD. However, the only true existing diagnosis is madeby pathologic examination of postmortem brain tissue in conjunction witha clinical history of dementia. This diagnosis is based on the presencein brain tissue of neurofibrillary tangles and of neuritic (senile)plaques, which have been correlated with clinical dementia. Neuriticplaques are made up of a normally harmless protein called amyloid-beta.Before neurons begin to die and symptoms develop, plaque deposits formbetween neurons early on in the disease process. The neurofibrillarytangles are interneuronal aggregates composed of normal and pairedhelical filaments and presumably consist of several different proteins.The internal support structure for brain neurons depends on the normalfunctioning of a protein called tau. In Alzheimer's disease, threads oftau protein undergo alterations that cause them to become twisted. Theneurohistopathologic identification and counting of neuritic plaques andneurofibrillary tangles requires staining and microscopic examination ofseveral brain sections. However, the results of this methodology canwidely vary and is time-consuming and labor-intensive.

[0009] Given the ability of both current and prospective pharmacologicaltherapies to forestall and/or reverse the onset and/or progress ofAlzheimer's dementia, it behooves us to promulgate interim methodologiesto delay the irreversible loss of cognitive function.

[0010] Various biochemical markers for AD are known and analyticaltechniques for the determination of such markers have been described inthe art. As used herein the term “marker” “biochemical marker” or“marker protein” refers to any enzyme, protein, polypeptide, peptide,isomeric form thereof, immunologically detectable fragments thereof, orother molecule that is released from the brain during the course of ADpathogenesis. Such markers may include, but are not limited to, anyunique proteins or isoforms thereof that are particularly associatedwith the brain.

[0011] The markers particularly targeted according to the method of theinvention are glial fibrillary acidic protein (GFAP) andglyceraldehyde-3-phosphate dehydrogenase (GAPDH).

[0012] Glial fibrillary acidic protein is an intermediate filamentprotein found almost exclusively in astrocytes which, in adults, controlthe level of GFAP expression. Astrocytes are a major type of glial cellwhich perform a variety of structural and metabolic functions, such asprocessing neurotransmitters, controlling extracellular ion levels,regulating the direction and amount of nerve growth, maintaining theblood-brain barrier, and participating in immune reactions. Asastrocytes transform from a resting state into a process-bearingreactive state during events such as aging, GFAP expression isup-regulated. Since levels have been found to increase in the braintissue and cerebrospinal fluid in patients suffering from AD, it hasbeen suggested that reactive astrocytes may contribute to theneuropathology of AD (Wallin et al. Dementia, 7, 267 (1996)). In the ADbrain, the loss of synapses is associated with an increase in the numberof GFAP-positive astrocytes. In addition, this loss of synapses appearsto be related to the extent of reactive astrogliosis (Brun et al.,Neurodegeneration, 4, 171 (1995)). GFAP is a major component of thegliotic scars which result from gliosis, and which may interfere withsubsequent reinnervation.

[0013] Glyceraldehyde-3-phosphate dehydrogenase is ubiquitous in thecell, with the major fraction in the cytoplasm associated withcytoskeletal proteins and membranes, and small amounts in the nucleus(van Tuinen et al., J. Histochem. Cytochem., 35 (1987)). Its size hasbeen characterized in the prior art as between 35,000 to 38,000 Daltons.As a monomer, GAPDH promotes tubulin polymerization, the majorconstituent of microtubules (Durrieu et al., Arch. Biochem. Biophys.,252, 32 (1987)). GAPDH has many enzymatic and binding activitiesincluding forming complexes with the C-terminal region of the amyloidprecursor protein (Schulze et al., J. Neurochem., 60 (1993)). Thedisruption in binding of GAPDH to cytoskeletal elements such as tubulincan result in the alteration of neuronal morphology, function, andsurvival. Its involvement in the neurodegeneration during thedevelopment of AD has been hypothesized due to its link to amyloidplaques (Sunaga et al., Neurosci. Lett., 200, 2 (1995)).

[0014] If treatment techniques for the removal of autoantibodiesassociated with biochemical markers for AD could be provided, physicianswould achieve an enhanced ability to circumvent, or delay, loss ofcognition at an early stage in the pathogenesis of this disease.

[0015] Certain types of treatment devices are known to be useful for theremoval of biological markers. Removal of these markers is also known tobe a valuable tool for reducing the manifestations of diseaseprogression.

[0016] What is lacking in the art is a method and device thereforeffective for treating Alzheimer's dementia in living patients alone, orin conjunction with, the use of pharmaceutical agents.

DESCRIPTION OF THE PRIOR ART

[0017] Generally, most scientific papers tend to focus on the peptide,β-amyloid, since it is postulated to be a major determinant of AD. Thisis supported by the observation that certain forms of familial ADmutations result in the over production of β-amyloid, particularly thelonger form (1-42) which aggregates more readily than the shorter form.Hensley et al. (Proc. Natl. Acad. Sci., (1994), 91, pp3270-3274) examinethe neurotoxicity based on free radical generation by the peptideβ-amyloid in its aggregation state. Several synthetic fragments of thepeptide are tested for resulting neurotoxicity. Based on the fact thatoxygen seems to be a requirement for radical generation and glutamatesynthetase and creatine kinase enzymes are oxidation-sensitivebiomarkers, the inactivation of these enzymes are utilized as indicatorsof active attack on biological molecules by these fragmented β-amyloidaggregates.

[0018] In U.S. Pat. No. 5,004,697, Pardridge describes the use ofmodified antibodies for treatment and diagnosis of neurologicaldiseases. A diagnostic composition is claimed involving an antibodycapable of binding to antigens present in GFAP protein or an antibody toan Alzheimer's disease amyloid peptide. Delivery of these antibodiesacross the blood-brain barrier (BBB) is essential to the Pardridgeinvention in order to achieve the diagnostic and/or therapeuticefficacy. Pardridge therefore requires modification of the antibodies byprocess of cationization. There is no disclosure regarding the removalof circulating autoantibodies as a treatment method.

[0019] In U.S. Pat. No. 5,627,047, Brenner et al teachesastroctye-specific transcription of human genes. GFAP is acknowledged inthe evaluation of AD, specifically the gene which encodes GFAP, howeverthe patent is silent regarding autoantibodies to GFAP.

[0020] U.S. Pat. No. 6,187,756, a divisional of U.S. Pat. No. 6,043,224,issued to Lee et al. describes a method of alleviating the negativeeffects of a neurological disorder or neurodegenerative disease. Themanner of alleviation is by administration of an antagonist of aβ-adrenergic receptor coupled to cAMP or the administration of a proteinkinase A or C signaling agent, for example. The importance of GFAP isonly seen as it relates to cAMP; GFAP expression in astrocytes isincreased by elevation in cAMP levels. Neither GFAP nor its autoantibodyare recognized as a tool in the treatment of AD.

[0021] U.S. Pat. No. 5,723,301 issued to Burke et al. teaches a methodto screen compounds that affect GAPDH binding to polyglutamine. The roleof GAPDH in neuronal death as a result of brain injury is described.Although a link of GAPDH to Alzheimer's disease is disclosed, theinterest lies only in polyglutamine regions. Neither GAPDH nor itsautoantibody are recognized as a target useful for direct interventionin the disease.

[0022] Many scientists have explored the significance of myelin basicprotein, neuron specific enolase, and S100 autoantibodies in AD. As faras GFAP, there are conflicting results and opinions regarding thesignificance of serum autoantibodies against this protein. Although ithas been suggested that the presence of anti-GFAP autoantibodies isrelated to Alzheimer's dementia, it is only as a secondary response.Generally, when GAPDH is utilized in Alzheimer's work, it is as ahousekeeping gene or mRNA probe for other proteins of interest in thedisease. Nothing in the prior art would suggest that a reduction in theamount of circulating autoantibodies to GFAP and GAPDH could have abeneficial effect in retarding the manifestations of Alzheimer'sdementia. In addition, it has not been previously suggested to removethe circulating autoantibodies associated with these proteins toalleviate symptoms of the disease state.

SUMMARY OF THE INVENTION

[0023] The present invention is directed toward a process and a devicewhich aids in the treatment of Alzheimer's dementia. Although notwishing to be bound to any particular theory or hypothesis, the instantinventors have recognized what appears to be a causal relationshipbetween the presence of certain autoantibodies, particularly those whichbind to GAPDH and GFAP in circulating sera, and the progressive loss ofcognitive ability associated with AD. It is therefore theorized thatreduction of these autoantibodies within the circulating sera, as a soletherapeutic modality or alternatively in conjunction with pharmacologictherapeutic agents, e.g. acetylcholinesterase inhibitors, would beeffective to mitigate the course of the disease, such mitigationincluding but not limited to retardation of disease progression and/orincrease of the period of efficacy of adjunct therapy. To this end, itis proposed to create a device to facilitate antigen-antibodyinteraction by creating an interfacial area containing a population ofimmobilized proteins which bind to the targeted autoantibodies. Theseimmobilized proteins, which function as a ligand, may be attached invarious ways to a base, e.g. polystyrene, silicone, silica, orsepharose. The proteins may be oriented or non-oriented, fashioned insome orderly mode of attachment or alternatively by means of a singlepoint attachment or flexible attachment to improve the accessibility ofthe binding site. Illustrative, but non-limiting means of attachment mayinclude the use of histidine residues for immobilization of proteins onvarious metal-chelate supports (Ho 1998); protein/autoantibodyinteraction (Kann 2000), and avidin-biotin mediated immobilization(Patel 2000).

[0024] Alternative forms of immobilized protein devices for bloodtreatment may include functionalized hollow fiber cartridges containingthe immobilized protein therein and capable of removal of autoantibodiesby adsorption from blood which is allowed to flow through the cartridges(Legallais et al. 1999). Processes for extracorporeal immunoadsorptionhave been disclosed for treatment of diseases such as rapidlyprogressive glomerulonephritis, recurrent glomerular sclerosis, systemiclupus erythematosus, cancer, myasthenia gravis, Guillain-Barré Syndromeand hemophilia.

[0025] What has not heretofore been known in the art is that a diseaseprocess which occurs behind the blood-brain barrier, such as Alzheimer'sdementia, could be effectively mediated by removal, from circulatingbody fluids, of those autoantibodies directly associated with reductionin cognitive ability associated with the disease.

[0026] The advantages which flow from the use of biological markers astreatment targets include strengthening the effectiveness ofpharmaceutical agents, and assisting in slowing down the rate of diseaseprogression.

[0027] Accordingly, it is an objective of the instant invention toprovide a process effective for delaying, reducing and/or retarding theloss of cognitive ability associated with the progression of Alzheimer'sdisease.

[0028] It is a further objective of the invention to provide a methodwhich includes analysis of at least one body fluid of a patient todetermine the presence of at least one marker indicative of Alzheimer'sdementia.

[0029] It is a still further objective of the instant invention toprovide an immunoassay effective for the recognition of autoantibodieslinked to the progression or manifestation of Alzheimer's dementia.

[0030] It is a still further objective of the invention to provide atest kit for gauging the progression or retardation of AD comprising anon-invasive point-of-care test which can be performed utilizing asample comprising blood or any blood product.

[0031] It is yet a still further objective of the instant invention toprovide a process and a related device effective for the selectiveremoval of at least one antibody linked to the progression and/ormanifestation of Alzheimer's dementia.

[0032] Other objects and advantages of this invention will becomeapparent from the following description taken in conjunction with theaccompanying figures wherein are set forth, by way of illustration andexample, certain embodiments of this invention. The figures constitute apart of this specification and include exemplary embodiments of thepresent invention and illustrate various objects and features thereof.

BRIEF DESCRIPTION OF THE FIGURES

[0033]FIG. 1 is of Western blots of brain tissue extracts comparingproteins found in AD brain to normal brain;

[0034]FIG. 2 is of 2D gels of brain extract from FIG. 1 highlighting theproteins of interest found in AD brain only.

DETAILED DESCRIPTION OF THE INVENTION

[0035] The markers which are targeted according to the method of theinvention are those which are released into the circulation as aconsequence of disease state and may be present in the blood or in anyblood product, for example plasma, serum, cytolyzed blood, e.g. bytreatment with hypotonic buffer or detergents and dilutions andpreparations thereof, and other body fluids, e.g. CSF, saliva, urine,lymph, and the like.

[0036] For some markers, detectable levels of the marker are presentnormally in an individual. However, in response to a variety ofphysical, chemical, and etiologic insults such as brain injury, ordisease, i.e. Alzheimer's, epilepsy, and multiple sclerosis, theselevels become elevated due to a modification of stimulation, ultimatelycausing neuronal dysfunction and death.

[0037] Western Blotting

[0038] With reference to FIG. 1, tissue samples are obtained postmortemand are stored frozen until use. For experimental preparation, tissuesamples are thawed and minced with a scalpel and subsequentlytransferred to glass tubes. A solution of phosphate buffered saline(PBS) containing a protease inhibitor cocktail, is added to the mincedtissue, then homogenized using a polytron homogenizer. A detergent(Triton X100) is added to the homogenization buffer to enhance theextraction of proteins that are normally associated with cell membranes.The crude homogenate is centrifuged at 10,000 RPM in a refrigeratedsuper-speed centrifuge to remove unbroken cells and cell debris whichform a pellet. The pellet is extracted two more times by resuspendingthe pellet in the homogenization buffer and centrifugation as describedabove. The tissue extract containing the proteins is further subjectedto electrophoresis on a polyacrylamide gel (12.5%) containing SDS andDTT to denature all the proteins. Following electrophoresis, theproteins are transferred onto a membrane (PVDF), blocked overnight with5% Blotto/50 mM Tris Buffered Saline (TBS) pH7.4 at 4° C. and incubatedwith serum from patients diagnosed with Alzheimer's Disease for a periodof 1 hour. After this incubation, the membrane is washed with TBScontaining 0.05% Tween 20 (TTBS); and a solution containing thesecondary antibody (goat anti-human IgG) conjugated to alkalinephosphate is added and incubated for an additional 2 hours. Followingthis incubation, the membrane is washed and the substrate (BioRad'salkaline phosphate substrate kit) is added which initiates the reactionfor color development. Rinsing with ultra pure water terminates thereaction. The membrane is allowed to air dry, then is photographed. Thephotograph is then analyzed using specialized software to identify theprotein bands that are present.

[0039] 2D-Gel Electrophoresis

[0040] With reference to FIG. 2, brain tissue extracts are separated byisoelectric focusing (IEF) using the Novex IEF gel system (pH gradient3-10) for the first dimension. Proteins are further separated bySDS-PAGE (12.5% acrylamide) for the second dimension. Gels are thenstained using Coomassie Blue stain and appropriately destained to removebackground. Gels are imaged using a camera connected to a computer.

[0041] Protein ID

[0042] Spots of interest are physically cut out of the gel (seearrows—FIG. 2) using a scalpel and placed in individual tubes. Gelpieces are dehydrated to remove water, making it easier for the trypsinenzyme to penetrate the gel and digest the proteins. The gel pieces areincubated overnight (16 hours) at 37° C. with the trypsin. An aliquot ofthe trypsin digest fluid is removed and an initial separation step isconducted using Millipore's C18 zip tips. The filtrate is then spottedonto Ciphergen's NP1 chips and peptide sequencing is conducted. Atrypsin blank is included on a blank piece of gel to enable a comparisonof the peptide map of trypsin cleaving itself versus the protein ofinterest.

[0043] The sequences identified from the two spots cut out are GAPDH andGFAP; the upper band on the 2D gel (FIG. 2) corresponds to the sequenceof GFAP and the lower band corresponds to GAPDH. It is apparent thesebands do not appear on the normal brain extract 2D gel which wouldsuggest these proteins play a role in the pathogenesis of AD.

[0044] The presence of antigen-presenting, HLA-DR-positive and otherimmunoregulatory cells, components of complement, inflammatory cytokinesand acute phase reactants have been established in tissue of ADneuropathology. Although the data do not confirm the immune response asa primary cause of AD, they indicate involvement of immune processes atleast as a secondary or tertiary reaction to the preexisting pathogenand point out its driving-force role in AD pathogenesis (Popovic et al.,Int. J. Neurosci., 95, 3-4, (1998)).

[0045] In a further contemplated embodiment of the invention, a methodof immune system modulation can be employed utilizing a patient's ownimmune system to specifically target autoantibodies of interestassociated with AD to be attacked and eliminated. It has long been knownin the prior art to incorporate an individual's own T-lymphocyte cellsto kill tumor cells. Only recently has this type of therapy demonstratedsuccess. By focusing on proteins particularly expressed by thebiochemical markers of interest, antigen-presenting cells with thisprotein particularly expressed on its surface can bind to CD28 on theT-cell surface to then induce the cascade of events, ultimatelyeliminating cells expressing the protein particularly expressed. Incurrent strategies, single chain antibodies are fused to the saidprotein particularly expressed by a cell type of interest assisting inthe T-cell activation process.

[0046] The level of any one or all of the specific markers of interestfound in the patient's body fluid may be used for purposes of monitoringremoval efficiency. Body fluid samples may be taken from a patient atone point in time or at different points in time for ongoing analysis.Typically, a first sample is taken from a patient upon presentation withpossible symptoms of AD and analyzed for presence of the particularmarkers. By “sample” is meant a body fluid such as blood. All themarkers can be measured with one assay device or by using a separateassay device for each marker in which case aliquots of the same samplecan be used. It is preferred to measure each of the markers in the samesingle sample, irrespective of whether the analyses are carried out in asingle analytical device or in separate devices so that the level ofeach marker simultaneously present in a single sample can be used toprovide meaningful data.

[0047] The presence of each marker is determined using antibodiesspecific for each of the markers and detecting specific binding of eachantibody to its respective marker. Any suitable direct or indirect assaymethod may be used, including those which are commercially available todetermine the level of each of the specific markers measured accordingto the invention. The assays may be competitive assays, sandwich assays,and the label may be selected from the group of well-known labels suchas radioimmunoassay, fluorescent or chemiluminescence immunoassay, orimmunoPCR technology. Extensive discussion of the known immunoassaytechniques is not required here since these are known to those ofskilled in the art. See Takahashi et al. (Clin Chem 1999;45(8):1307) forS100B assay.

[0048] All patents and publications mentioned in this specification areindicative of the levels of those skilled in the art to which theinvention pertains. All patents and publications are herein incorporatedby reference to the same extent as if each individual publication wasspecifically and individually indicated to be incorporated by reference.

[0049] It is to be understood that while a certain form of the inventionis illustrated, it is not to be limited to the specific form orarrangement of parts herein described and shown. It will be apparent tothose skilled in the art that various changes may be made withoutdeparting from the scope of the invention and the invention is not to beconsidered limited to what is shown and described in the specificationand drawings.

[0050] One skilled in the art will readily appreciate that the presentinvention is well adapted to carry out the objects and obtain the endsand advantages mentioned, as well as those inherent therein. Theoligonucleotides, peptides, polypeptides, biologically relatedcompounds, methods, procedures and techniques described herein arepresently representative of the preferred embodiments, are intended tobe exemplary and are not intended as limitations on the scope. Changestherein and other uses will occur to those skilled in the art which areencompassed within the spirit of the invention and are defined by thescope of the appended claims. Although the invention has been describedin connection with specific preferred embodiments, it should beunderstood that the invention as claimed should not be unduly limited tosuch specific embodiments. Indeed, various modifications of thedescribed modes for carrying out the invention which are obvious tothose skilled in the art are intended to be within the scope of thefollowing claims.

what is claimed is:
 1. A process for mitigating the progression ofAlzheimer's dementia (AD) comprising: determining the presence incirculating body fluid of at least one biochemical marker indicated inthe progression of AD; and removing an amount of said at least onemarker effective to mitigate said disease.
 2. The process of claim 1wherein said step of removing includes at least one method selected fromthe group consisting of extracorporeal immunoadsorption, plasmaphoresis,hemophoresis, plasma exchange, and immune system modulation.
 3. Theprocess of claim 1 wherein said biochemical marker is at least onemarker selected from the group consisting of autoantibodies to humanglial fibrillary acidic protein (GFAP) and glyceraldehyde-3-phosphatedehydrogenase (GAPDH).
 4. A device for mitigating the progression ofAlzheimer's dementia (AD) comprising: means for removal of at least onemarker from circulating body fluid whereby said removal includes captureof protein specific antibodies.